Solar Heat Panels

bobnamy

Well-known member
May 3, 2008
45
rock springs, wi
#1
There are several common brands - Sun Heater, Sun Grabber, etc., that all seem to have the same basic construction. Are there any obvious, practical differences?

I will be having 4 or 3 2 foot panels on my system for a 27' AGP. The panels will be located at ground level right next to the pool. I have heard that this will not increase the head factor becuse there is no lifting of water. But what about resistance to flow? Won't these panels slow down the movement of the water by increasing resistance?

How do I account for solar panels in choosing a pump? At this point I am looking at a 1/2 or 3/4 hp single speed pump, but I have not been able to determine what effect the solar panels will have on the pump choice. Any help is appreciated.
 

FordPrefect

LifeTime Supporter
Apr 29, 2008
17
Manitoba, Canada
#2
We bought the 3 panel 2'x20 SunGrabber panel kit with our pool, I got it hooked up yesterday and there is a noticeable drop in flow. The pressure gauge on the filter jumped from 9 psi to 17 psi and the water volume through the return dropped a lot.

However, the water was warmer coming through the return, so the panels are working :)

I am hoping this is normal.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
31,333
Sebring, Florida
#3
The guru, mas985, is still sleeping out on the west coast :lol: I'll just chime in briefly to confirm your thinking.

It IS the resistance to flow that increases your head and not the height of the panels. The panel height is essentially irrelevant.

Fordprefect's experience of increased psi and lower flow is normal and common
 

bobnamy

Well-known member
May 3, 2008
45
rock springs, wi
#5
Well then, from what I understand about pump/pipe dynamics (virtually nothing), then it would seem that a 1/2 hp pump would be better than a 3/4. as I believe there is little to be gained from a stronger pump pushing harder for deminimus increase in flow.

But, this logic opens up a new possibilty. I had actually ruled out a 3/4 hp 2 speed pump because the 25 gpm on low speed seemed too low. But maybe the lower gpm would be better with the solar panels. I would need a longer run time (11 hours to turn over pool) but at least I would have the high speed available to increase flow bypassing the solar panels and vaccumimg, etc.

What do you think about the 2speed pump idea?
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,879
Silver Spring, MD
#6
One key question is the height of the panels relative to the pool water. Panels near the level of the pool are fine with a small pump and/or low speed. But panels well above the level of the pool need high speed on a not extremely small pump to prime properly.
 

bobnamy

Well-known member
May 3, 2008
45
rock springs, wi
#7
The panels will be sitting on the ground, tilted slightly up on a rack to get the best exposure. The top of the panels will be at or below the top level of the pool water. I am thinking the 3/4 hp 2 spd pump will be a good choice. It will not be wasting power pushing into the highly restricted panels, and the high speed will not exceed the maximim flow of the 22" sand filter. Thus, if I ever need to turn over the water quickly, I will have that option. Plus, the solar panels will not be operating all of the time.
 

dschlic1

LifeTime Supporter
Oct 5, 2007
561
Valrico, FL
#9
One important thing to keep in mind with solar panels is that they have an optiuium flow point. For example my panels should have a flow of 6 gpm each for best results. As I have four panels this means a total of 24 gpm should flow through my solar array. As my pump produces about 75 gpm at high speed, my setup has a bypass for most of the flow around the array.
 

nivek911

LifeTime Supporter
May 13, 2007
21
#10
Interesting point dschlic1. I added a 4x20 one piece panel to our pool this spring (ground level). I have a 1 hp single speed Hayward pump which pumps about 50-75gpm. The pressure on the sand filter shows a gain of about 2 lbs. The manual for the panel states the increase should be no more than 3-4 lbs. There is no mention of the GPM flow to be directed through it, so I currently have it set to full deflection on the valve.

The last full sunny day, I jumped from 74 to 82 degrees, so it appears to be working. I'm curious why Ford's panels add so much more pressure and should I not be pumping so many GPM through the panel?
 

Jond

Member
Jun 17, 2007
14
S.Tx
#11
bobnanny

I run 4 2X20 sunheaters in parallel with a 1 HP 2 speed pump. My heaters have a separate return that goes over the top and heaters are on the ground. I use 2 ball valves to help control rate, one full open to heaters and the normal return to the pool 7/8 open. This gives me optimal flow rate for my configuration on low speed. I rarely run my pump on high but when I do I close my heater valve.

My next purchase will be a solar controller with a 2 way valve actuator. My pool ran away and got to 100°F last month, what a hot tub. LOL.
 

FordPrefect

LifeTime Supporter
Apr 29, 2008
17
Manitoba, Canada
#12
nivek911 said:
I'm curious why Ford's panels add so much more pressure and should I not be pumping so many GPM through the panel?
I am guessing that I need to put in a bypass as well. Would it be as simple as T-ing in a shutoff valve between the inlet and outlet pipes right before the panels or do I need to buy something else?
 

Jond

Member
Jun 17, 2007
14
S.Tx
#14
An actuator can electrically open or close valves, in my case I want to use on a 2 way valve, 1 inlet and 1 outlet, i.e a normal valve. There are only certain valves that accept actuators. Most solar system setups use a 3-way valve(1 inlet and 2 outlets). 1 outlet to the pool return and the other outlet to the solar panels . I don't like the 3 way because of the all or nothing flow to the solar panels, hence my reason for wanting an actuator to open a 2 way, since mine is piped with a bypass. Not having own/operated/installed an actuator system I am sure the 3 valve can be setup not to fully close by the adjustments of the limits on the actuator to give you flow adjustment, but I don't believe they are designed as such.

I will have to change out the bottom valve on my system pictured below with a jandy valve to take the actuator and run my pump during the day and just have the controller open the valve to the solar panels when temperatures are right.

The picture shows 2 panels, have since added 2 more.
 

Attachments

Titanium

LifeTime Supporter
Jun 26, 2007
441
SF Bay Area
#15
Jond,

I don't like the 3 way because of the all or nothing flow to the solar panels, hence my reason for wanting an actuator to open a 2 way, since mine is piped with a bypass.
It doesn't have to be all or nothing with a three-way valve. http://www.powermat.com/PG5ht.html shows a setup using a 3-way valve and utilizing a bypass such that the solar panels are not "all or nothing".

Titanium